Touchscreen displays are able to detect a touch such as by a finger or stylus within an active or display area. Use of a touchscreen as part of a display enables a user to interact with an electronic application by touching the touchscreen. The display may present images to the user. Such images may include user interface constructs such as different buttons, images, or other regions that can be selected, manipulated, or actuated by touch. Touchscreens can therefore provide an effective user interface for cell phones, GPS devices, personal digital assistants (PDAs), computers, ATM machines, and other such devices.
Touchscreens use various technologies to sense touch from a finger or stylus, such as resistive, capacitive, infrared, and acoustic sensors. In one type of capacitive sensor based touchscreen, a touch changes a capacitance at a node in an array of electrodes overlaying the display device. Capacitive touchscreens often use one or more layers of transverse electrodes, drive electrodes and sense electrodes, separated by a dielectric. The intersections of the transverse electrodes form the nodes. Electronics may be used to drive a series of pulses of current on the drive electrodes. Charge at the nodes accumulating during each pulse is then captured, and used to determine the location of a touch or touches.
Transparent conductors such as indium tin oxide (ITO) or transparent conductive polymers may be used to form the electrodes. Some layouts of electrodes utilize a flooded type pattern of drive electrodes to shield the sense electrodes from electric field interference from an underlying display, such as a liquid crystal display (LCD). The flooded type pattern uses solid fill closely spaced adjacent drive electrode patterns and is formed in a layer between the sense electrodes and display.
In some prior touchscreen devices, the layer of electrodes closest to the LCD, are the drive electrodes, and run in a first direction. The sense electrodes included spines that run transverse to the drive electrodes, and also include cross bars that run in the same direction as the drive electrodes. The cross bars may be used to increase the distance between the sense electrodes such that larger touchscreens may be provided without increasing the number of sense electrodes. However, the cross bars add resistance and parasitic capacitance, as well as complexity to the electrode layout.